Acceleration sensor

Abstract

The present disclosure provides an acceleration sensor. The acceleration sensor includes: a substrate; a first mass portion supported by the substrate so as to be movable along a thickness direction of the substrate; and a beam portion supporting the first mass portion on the substrate. The beam portion includes: a second mass portion having a mass less than a mass of the first mass portion; a first spring portion connecting the first mass portion with the second mass portion; and a second spring portion having a spring constant smaller than a spring constant of the first spring portion and connecting the second mass portion with the substrate. A movable electrode of a sensor element is disposed on the second mass portion and configured to detect an acceleration along the thickness direction of the substrate. A fixed electrode of the sensor element is disposed on the substrate.

1 . An acceleration sensor, comprising:
 a substrate; and   a first mass portion, supported by the substrate so as to be movable along a thickness direction of the substrate; and   a beam portion, supporting the first mass portion on the substrate, wherein   the beam portion includes:
 a second mass portion, having a mass less than a mass of the first mass portion; 
 a first spring portion, connecting the first mass portion with the second mass portion; and 
 a second spring portion, having a spring constant smaller than a spring constant of the first spring portion and connecting the second mass portion with the substrate, wherein 
 a movable electrode of a sensor element is disposed on the second mass portion and configured to detect an acceleration along the thickness direction of the substrate, and 
 a fixed electrode of the sensor element is disposed on the substrate. 
   
     
     
         2 . The acceleration sensor of  claim 1 , wherein
 the movable electrode includes a movable electrode portion formed in a comb-teeth shape, and   the fixed electrode includes a fixed electrode portion formed in a comb-teeth shape.   
     
     
         3 . The acceleration sensor of  claim 2 , wherein the movable electrode portion and the fixed electrode portion are arranged to face each other along a direction perpendicular to the thickness direction of the substrate. 
     
     
         4 . The acceleration sensor of  claim 1 , wherein
 the substrate has a cavity partially exposed on a surface, and   the first mass portion and the beam portion are provided on the substrate to be disposed within the cavity.   
     
     
         5 . The acceleration sensor of  claim 1 , wherein
 the acceleration sensor includes a plurality of the beam portions, and   the plurality of beam portions are evenly arranged around the first mass portion in a plan view.   
     
     
         6 . The acceleration sensor of  claim 5 , wherein
 the acceleration sensor includes two of the beam portions, and   the two beam portions are formed symmetrically with the first mass portion in between.   
     
     
         7 . The acceleration sensor of  claim 5 , wherein the acceleration sensor includes four of the beam portions. 
     
     
         8 . The acceleration sensor of  claim 1 , comprising a direction detection mechanism configured to detect an acceleration direction along the thickness direction of the substrate. 
     
     
         9 . The acceleration sensor of  claim 8 , wherein
 the movable electrode is a movable electrode for acceleration detection,   the fixed electrode is a fixed electrode for acceleration detection,   the direction detection mechanism includes a movable electrode for direction detection and a fixed electrode for direction detection configured to detect the acceleration direction along the thickness direction of the substrate,   the movable electrode for direction detection is disposed on the first mass portion, and   the fixed electrode for direction detection is disposed on the substrate.   
     
     
         10 . The acceleration sensor of  claim 9 , wherein the movable electrode for direction detection and the fixed electrode for direction detection include:
 an overlap region, where positions along the thickness direction of the substrate overlap; and   a non-overlap region, where positions along the thickness direction of the substrate do not overlap.   
     
     
         11 . The acceleration sensor of  claim 9 , comprising:
 a first sensor element, configured to detect acceleration along a first direction that is the thickness direction of the substrate; and   a second sensor element, configured to detect acceleration along a second direction perpendicular to the first direction, wherein   the second sensor element includes:
 a movable electrode for acceleration detection, disposed on the first mass portion; and 
 a fixed electrode for acceleration detection disposed on the substrate, and wherein 
   the movable electrode for direction detection and the fixed electrode for direction detection comprise the movable electrode for acceleration detection and the fixed electrode for acceleration detection of the second sensor element.   
     
     
         12 . The acceleration sensor of  claim 9 , comprising:
 a first sensor element, configured to detect acceleration along a first direction that is the thickness direction of the substrate;   a second sensor element, configured to detect acceleration along a second direction perpendicular to the first direction; and   a third sensor element, configured to detect acceleration along a third direction perpendicular to the first direction and the second direction, wherein   each of the second sensor element and the third sensor element includes:
 a movable electrode for acceleration detection, disposed on the first mass portion; and 
 a fixed electrode for acceleration detection disposed on the substrate, and wherein 
   the movable electrode for direction detection and the fixed electrode for direction detection comprise the movable electrode for acceleration detection and the fixed electrode for acceleration detection of at least one of the second sensor element and the third sensor element.